1) Let the mondo dock grow symmetrically from the center as you add
more icons to it (possibly optional)
2) Let folders in the mondo dock be able to accept items dropped into
them (would be really useful)
3) The GUI would look nicer if the icons were center-aligned vertically
4) Opaque dock colors (maybe a checkbox for
this option that affects all colors)
5) Since the mondo dock lives in the dashboard world, there is really
no need to limit the number of icon rows to just one. Maybe it could
be resizable into any rectangular shape.
6) It would be nice if running applications were indicated somehow
(triangle below?)

[quote]1) Let the mondo dock grow symmetrically from the center as you add
more icons to it (possibly optional) [/quote]

There's no officially supported way to make a widget grow anyway other than down and to the right (there are undocumented ways, but those aren't guaranteed to work).

[quote]2) Let folders in the mondo dock be able to accept items dropped into
them (would be really useful)
[/quote]
That's a good idea, and shouldn't be too tricky to hand off copying to the Finder.

[quote]3) The GUI would look nicer if the icons were center-aligned vertically
[/quote]
Not sure what you mean by this - assuming you mean a vertical oriented item, the space those button that appear next to the icon?

[quote]4) Opaque dock colors (maybe a checkbox for
this option that affects all colors) [/quote]
I think it can already do that, but I don't have opaque colors in the color list (i.e, it's just a matter of adding them, and everything should work).

[quote]5) Since the mondo dock lives in the dashboard world, there is really
no need to limit the number of icon rows to just one. Maybe it could
be resizable into any rectangular shape. [/quote]
I'm avoiding this one because it causes all sorts of problems - with a 1xN (or Nx1) list there are no issues with "blank" cells, no resizing problems (i.e., you might want to shrink a 2x4 grid down to 1x8 but you can't go from 2x4 to 1x4 because you'd loose half the icons, so you'd first need to stretch 2x4 to 2x8 and then down to 1x8).

I originally envisioned something like that, but I like the "add an item and it grows to show it" model.

[quote]6) It would be nice if running applications were indicated somehow
(triangle below?) [/quote]
Definitely seems possible. It would also be nice to be able to grab the "badged icon" (like the numbers by mail, for example) but that information isn't publicly available (since the badging involves private communications between the application and the dock).